Research Cases

Case law

"Case law" is all of the previous decisions made by judges. It is created by judges in their rulings when they write their decisions and give the reasoning behind them. These decisions are often called "opinions" and, in them, judges often cite precedents from other cases and statutes that influenced their decisions. These opinions form the principles that a court will normally consider when interpreting the law. This is called "legal precedent" and is central to legal analysis and rulings.

State trial courts (superior courts) do not publish opinions, so their decisions are not generally used as "legal precedent." The bulk of published opinions come from state and federal appellate courts and the Supreme Court.

A court gives legal precedent more or less weight depending on a number of factors:

Most important is whether the precedent is "on point." Does it deal with a circumstance identical or very similar to the circumstance in your case?

Second, when and where was the precedent decided? A recent decision by the same appellate court that oversees the trial court where your case is being heard will be given great weight.

Next in importance is recent precedent by appellate courts for other areas (of the state or of the U.S.) whose law is the same as the law that your court follows.

The least weight is given to precedent that comes from cases where the circumstances were different from your case, from older cases that have since been contradicted, or from cases in geographical areas or courts that have law that is considerably different from the law in the court your case is in.

Finding cases (also called "opinions")

When you researched practice guides, annotated codes and statutes, and self-help books, you probably saw and wrote down several references to cases that you want to look up because they are similar to your legal research issue and may help (or hurt) your own case. The references you have will look something like this:

Finding California court opinions online

You can also find past court cases or opinions in law libraries. To find cases in print at your local county law library, you can use a number of tools. If you know the name of the case, you can locate a table of cases that will list the cases alphabetically and give you the book, volume, and page where the case is located. If you have the citation, you can simply find the correct set of books, pull the volume, and turn to the page.

If you are looking for cases by topic, you can use a tool known as a “digest.” Digests are indexes to case law and also a way to find cases by topic, name, or subject. Digests are organized alphabetically by subject with numbers that classify the law into topics and subtopics.

Remember, cases with published opinions are Supreme Court or appellate cases, and these are the cases you can cite as authority in your case. And you can find them online or at your county law library. Superior or trial court cases cannot be cited as authority and are not published, so you cannot get them at your library. But if there is something about a superior court case that you think is helpful to you, you can find those decisions and court records in the superior court where the case was decided and sometimes online at that superior court’s website.

Finding federal court opinions online

The federal court system includes the Supreme Court of the United States, U.S. Courts of Appeals, U.S. District Courts, the U.S. Court of Federal Claims, U.S. Court of International Trade, U.S. Court of Appeals for the Armed Forces, and U.S. Bankruptcy Courts.

The U.S. Courts of Appeals consist of 11 circuit courts in addition to the District of Columbia Circuit and the Federal Circuit. California is in the Ninth Circuit along with Alaska, Arizona, Hawaii, Idaho, Montana, Nevada, Oregon, and Washington. Click for information about and opinions issued by the Ninth Circuit Court of Appeals. For information about the other circuits, you can go to your local public law library or use the Ask a Law Librarian service.